The present invention relates to plastic piping and, in particular, to reinforced composite pipe elements.
Plastic pipe elements, such as fittings, flanges, and caps, for example, have heretofore been fabricated using various techniques intended to provide a high-strength element presenting a continuous fluid-conducting surface which is resistant to chemical attack by the fluid being conducted. It has been proposed to form a fitting by molding such that the internal fluid-conducting portion thereof is a continuous and uninterrupted surface (no joints), but such a molding technique is relatively expensive. Additional techniques are disclosed in the following U.S. patents: U.S. Pat. No. 4,047,741 issued to Pertriaux on Sept. 13, 1977; Pat. No. 3,873,391 issued to Plauka et al on Mar. 25, 1975; Pat. No. 3,458,619 issued to Prochaska on Jul. 29, 1969; Pat. No. 2,503,882 issued to Medford on Apr. 11, 1950; Pat. No. 2,878,038 issued to Noland on Mar. 17, 1959; Pat. No. 3,312,765 issued to Scott on Apr. 4, 1967; and Pat. No. 3,235,289 issued to Jones on Feb. 15, 1966.
The Plauka et al patent relates to the fabrication of non-linear plastic pipe fittings. The technique disclosed therein involves mitering the edges of a plurality of plastic pipe sections so that when the mitered edges engage one another in complementary fashion, the pipe sections assume the shape of the desired fitting. The mitered edges are held in place while a liquid coating of an elastomeric resin such as a polyurethene elastomer is applied externally to form a permanent resilient coating or band.
The Prochaska patent relates to the fabrication of plastic fittings which two pipe sections are mitered and fitted on mandrels to form the desired fitting shape. The pipe sections are positioned in a high temperature and pressure mold while thermoplastic material is injected into the mold to surround the fitting joint. After the assembly is removed from the mold, the mandrels are withdrawn.
Pipes formed in the manner disclosed in Plauka et al and Prochaska would result in interfaces being created at the joints where the pipes abut, which interfaces are less resistant to chemical attack. Reinforcement can be provided by spraying or molding-on a liquid resin coating, but such a coating is not as strong as would be desired.
The Pertriaux patent relates to the fabrication of a plastic pipe fitting by providing a mandrel having the desired fitting shape and arranging glass fibers on the mandrel. The fibers and mandrel are encased within two half shells. A thermo-setting plastics material is injected into the half shells to coat the fibers. After the plastics material has set, the mandrel is removed.
The Noland patent relates to the fabrication of glass fiber reinforced plastic fittings. The technique involves the formation, in half sections, of a fitting formed of glass fiber reinforced resin material. After the half sections are fitted together, glass fiber is wound around the entire fitting and is then resin impregnated.
The Scott patent involves the fabrication of plastic pipe fittings. The technique involves forming straight sections of piping from a particle-formed polymeric material. These pipe sections are mitered and then installed on mandrels. The assembly is inserted in a high temperature pressure mold and fused. The mandrels are eventually withdrawn to produce the finished product.
The Jones patent relates to the formation of butt joints on plastic pipe. In this technique the pipe sections are cut square on the ends and abutted together. Pre-preged sheets of glass cloth impregnated with a thermal-setting resin are wrapped around the abutted ends. An irradiated polyethylene tape is spirally wound around the pre-preged sheet. The pre-preged tape-wrapped pipes are heated to cure the resin of the pre-preged sheet and bonded to the pipe sections.
Techniques such as disclosed above which involve extensive wrapping operations and/or the molding of a resin around formed parts, are relatively expensive, among other shortcomings. If joints are created which are exposed to the chemical being conducted, the fitting may be unduly susceptible to chemical attack.
It is, therefore, an object of the present invention to minimize or obviate problems of the type discussed above.
It is a further object of the invention to provide novel plastic pipe elements, such as fittings, flanges, and caps, and methods for producing same.
It is an additional object of the invention to provide novel composite plastic pipe elements which are durable, chemically resistant, and relatively inexpensive to manufacture.
A further object of the invention is to enable such elements to be formed without a manual filament winding operation.